This invention relates generally to video disc playback styli and particularly to such styli having a coated electrode for capacitive pickup video disc systems.
Video disc playback systems of a variable capacitance type are disclosed in U.S. Pat. No. 3,842,194 issued on Oct. 15, 1974 to Jon K. Clemens. Also disclosed in that patent and shown in FIG. 5 thereof is a stylus for playing back the recorded information. The disclosed stylus has a sapphire mounting structure with a conducting element deposited on one surface.
Difficulty is often encountered when the conducting element is deposited on the sapphire mounting structure. A metal film is often used as the conducting element. However, many desirable metal films have poor adherence to a polished sapphire surface. For example, it is difficult to deposit sufficiently adherent tungsten, hafnium or chromium films onto such a surface.